The present invention relates to the manufacture of integrated circuits. More particularly, the invention provides a technique including a method and an apparatus for chemical mechanical polishing using a device that maintains substantially parallel alignment between a surface of a film being polished and a rotating polishing surface, as well as other features. Among other benefits, parallel alignment tends to produce more uniformity in the film being processed and maintains film quality.
Chemical mechanical polishing or planarization (“CMP”) is a technique of polishing materials including semiconductor substrates and films overlying such substrates, which provides a high degree of uniformity and planarity. The process is used to remove high elevation features on films created during the fabrication of a microelectronic circuitry on the substrate, or to remove a layer of film to reveal the circuitry buried underneath the film. In some cases, the process can even planarize semiconductor slices prior to the fabrication of microelectronic circuitry thereon.
A conventional chemical mechanical polishing process uses an apparatus having a single large polishing pad positioned on a platen, against which a substrate is positioned for polishing. A positioning member positions and biases the substrate to be polished against the polishing pad, which is rotating. A chemical slurry, which is likely to have abrasive materials, is maintained on the polishing pad to modify the polishing characteristics of the polishing pad and to enhance the polishing of the substrate or films.
Unfortunately, chemical mechanical polishing is not free from limitations in the manufacture of integrated circuits. For instance, CMP is extremely time consuming, which generally influences wafer throughput. Additionally, the polishing pad often accumulates residual by-products from the polishing operation or wears and deforms the polishing pad, which leads to degradation of the polishing efficiency for the polishing operation. Furthermore, the apparatus with the single polishing pad can only perform a single process such as dielectric layer polishing or tungsten film polishing, thereby requiring an additional apparatus to perform other processes. Moreover, conventional CMP of large substrate surfaces tends to be problematic, since it is often difficult to maintain parallel alignment between a substrate surface and a rotating polishing surface using conventional techniques. Accordingly, conventional chemical mechanical polishing has a variety of limitations.
From the above, it is seen that a technique for chemical mechanical polishing which is cost effective and efficient is often desirable.